The present invention relates to a wet type image forming apparatus. More particularly, the present invention relates to a wet type color image forming apparatus which comprises a development means to which a plurality of liquid developers of a different color are selectively supplied to form a multicolored image.
A wet type development means for forming a colored image is widely applicable to various image forming apparatuses such as an electrophotographic copying apparatus and a facsimile system etc. In accordance with a generally used conventional wet type color image forming apparatus, the apparatus comprises one photoconductor unit which is provided with one development device and one cleaning device. The color image forming process is carried out in such a way that images of a different color are formed subsequently one after another on the photoconductor unit. More precisely, first, an optical image analyzed to a specified color is projected on the photoconductor unit to expose the same so that an electrostatic latent image corresponding to the specified color is formed on the photoconductor unit. After that the electrostatic latent image is developed so as to form a visual image by a color liquid developer corresponding to the specified color which developer is selectively supplied to the development device. After that the visual image is transferred to a transfer paper wound around a transfer drum. In this transferring process, some liquid developer is untransferred to the paper and remains on the photoconductor drum. Such untransferred developer remaining on the photoconductor drum is removed by the cleaning device. Each of the exposure process, the development process, the transferring process and the cleaning process mentioned above is carried out repeatedly for each of different colors to form a plurality of color images of a different color which images are superposed on each other to form a multicolored image.
Accordingly, the conventional color image forming apparatus requires a relatively long time for forming a colored image in comparison to a monochrome image forming apparatus since the image forming processes for different colors have to be repeated. In order to obviate this problem, there has been proposed an image forming apparatus which comprises a plurality of photoconductor units disposed side by side in series along a conveyor belt corresponding to different colors, respectively, each unit being provided with a wet type development device and a cleaning device wherein a transferring portion is arranged at a lower side of each photoconductor unit so that a plurality of the transferring portions are disposed in series along the conveyor belt having a longitudinal strip shape. In accordance with such a color image forming apparatus, a transfer paper is placed on and carried by the conveyor belt through the transferring portions where the images of a different color are transferred to the paper one after another in series one above the other so that a multicolored image is formed on the paper while passing through the transferring portions in one circulation of the conveyor belt. Therefore, it bocomes possible to reduce the time for forming the color image as short as a half or less as that of the conventional image forming apparatus so that a high speed operation can be achieved. Such a high speed color image forming apparatus is disclosed for example in Japanese Examined Patent Publication No. 55-6225 of the same applicant as that of the present application.
However, the above mentioned high speed color image forming apparatus has a problem that the liquid developer drips and falls from the development device or the cleaning device onto the transfer paper on the conveyor belt since the transferring portions are located at the lower side of the photoconductor unit, which impairs the quaility of the color image. Therefore, conventionally it has been difficult to realize the high speed wet type color image forming apparatus mentioned above.
A technique for preventing the liquid developer from dripping and falling from the development means is partly disclosed in U.S. Pat. No. 4,435,068. However, the technique does not fully satisfy the requirement for avoiding the drip of the liquid developer to upgrade the quality of the color image formed by the high speed type image forming apparatus using the liquid developer.